LNL Experimental set -up for thermal resistance at ...

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Experimental set-up for thermal resistance at interface measurements SARA CISTERNINO, HANNA SKLIAROVA, MATTEO GOBBO, CARLOS ROSSI ALVAREZ, ALESSANDRO ZANON, JUAN ESPOSITO LNL 22-09-2017

Transcript of LNL Experimental set -up for thermal resistance at ...

Page 1: LNL Experimental set -up for thermal resistance at ...

Experimental set-up for

thermal resistance at

interface measurements

SARA CISTERNINO, H A N NA S KL I A R OVA , M AT T E O GOB B O,

CA R LO S R O S S I A LVA R E Z , A L E S S AN DR O Z A N O N, J UA N E S P O S ITO

LNL

22-09-2017

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Cyclotron solid target station

TR19 target of Advanced Cyclotron Systems Inc.

TEMA target prototype St.Orsola Hospital, Bologna

80μA

300μA

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Solid target station: a technical design challenge

target

New high performance cyclotrons -> High radioisotopes yields -> heat power removal eng. issues

High heat power density hitting the target

p+

He Heat dissipation system

H2O

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How to dissipate the heat power? State of art: radioisotope solid target system

Open cooling system conf.

Direct more efficient cooling

X Potential loss of coolant

accident (LOCA)

Closed cooling system conf.

No water losses → higher safety

Possible different cooling sink geometry

X Target temperatures affected by

Thermal Contact Resistance at interface

Baseplate

Target material

Cooling system

Conductive heat transfer

Convective heat transfer Conductive

heat transfer

TCR

Convective heat transfer

Baseplate

Target material

Cooling system

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High power cyclotron solid target station

Main target station design input :

- Heat power removal : 30 kW

- Possible beam hitting configurations:

- Emax =70 MeV, Imin= 100 µA

- Emin =40 MeV, Imax =750 µA

Average beam power density of 1 kW/cm2 on the target

(reference target area spot size: 30 cm2)

LARAMED target system : main design goal

Preferred configuration: closed cooling system

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Thermal Contact Resistance at interface

Thermal Contact Resistance (TCR) depends on:

• materials

• surface roughness

• contact pressure

• oxidation level

Surface 1

Surface 2

Air

Surface in contact

The main problem to work out: Thermal Contact Resistance (TCR) at interface

Heat sink system

Target base plate

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Thermal Contact Resistance at interface Analytical model*

𝑇𝑇𝑇𝑇𝑇𝑇 = 1,55 𝑘𝑘𝑠𝑠𝑚𝑚𝜎𝜎

2𝑝𝑝𝑚𝑚𝐸𝐸′

0,94

TCC: Thermal contact conductance [W m-2 K-1]

ks: harmonic average of thermal conductivity of the materials [W m-1 K-1]

σ: RMS surface contact roughness [m]

m: slope of material asperity f(σ)

p: contact pressure [Pa]

E’: Young Modulus of the materials [Pa]

* A. Dall’Occhio, A. Bertarelli et al., “LHC Collimators: un modello agli elementi finiti per l’analisi termostrutturale”, Associazione italiana per l’analisi delle sollecitazioni (AIAS), XXXVI Convegno Nazionale

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Experimental set-up for TCR measurement

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Experimental set-up designed in order to measure Thermal Contact

Resistance (TCR) for real systems

• different target/heat sink materials (Cu-OFE /Al alloys, other materials)

• different surface finishing

(turning, grinding, lapping)

• different contact pressures

(1.3 – 4.2 MPa)

• different surface oxidation level

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Experimental set-up for TCR measurement

chiller

lamp power supply

flowmeter

Heater

thermocamera

Agilent

Flowmeter power supply

Samples

Piston pressure regulator

PC with data acquisition system

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Copper sample upper

Collimator

Graphite Insulator

Interface

Copper sample lower

Holes for thermo-couples Cooling system

Pneumatic piston

Cooled flange

Heater

Load cell

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Samples geometry chosen

4 K-Thermocouples

Different surface treatments at interface

TCR = 𝐴𝐴 ∆𝑇𝑇�̇�𝑞

𝑚𝑚2 𝐾𝐾/𝑊𝑊

Contact pressure

Axial temperature distribution

ANSYS thermal and structural FEM to get:

• a uniform contact pressure at interface

• a linear temperature distribution along the axis

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Pressure load system

FX1901 Compression Load Cell

Compressed air driven pneumatic piston to tune the samples contact pressure

Valve

Load cell to measure the force used to keep the samples pressed

Piston

Pressure regulator

Compressed air connection (max 7bar)

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Air pressure [bar] Contact pressure [Mpa] 2 1,3

3 1,9

4 2,5

5 3,1

6 3,6

7 4,2

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Air pressure – Contact pressure loads ranges

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Main Electric parameters

• Power supply voltage: 0-100 V

• Absorbed Power: 1 kW

IR output range

• Beam spot Ø15 mm

Declared beam power density

• approximately 124 W/cm2

Max. heating temperature: 1000 °C

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Heat source - IR lamp main data

Power supply

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Heat source- IR lamp

Use of collimator to focus the spot and

protect the eyes

Use of graphite disk to absorb better IR

(Cu and Al reflect IR light)

90

170

437

100

183

0

100

200

300

400

500

0 20 40 60 80 100

Tem

pe

ratu

re [

°C]

Lamp Voltage [V]

Estimation of graphite T vs Lamp voltage

contact pressure 4,3 MPa contact pressure 1,2 MPa

Graphite

Collimator

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Water cooling

Chiller

Cooling chamber in contact

with the lower sample

RTD sensors to acquire water

Inlet and Outlet temperature

Ultrasonic flowmeter to

control the water flow rate

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Data acquisition system

Agilent for board sensors connection

Program to record the data

• Agilent Vee pro+ • Labview • MatLab

Calibration of T sensors in respect to calibrated TC

• Error in Tc reading with Agilent vs channel

Agilent Vee pro+ LabView MatLab

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TCR estimation based on measured parameters

𝑄𝑄1 =𝑘𝑘 ∙ 𝐴𝐴 ∙ (𝑇𝑇1 − 𝑇𝑇2)

𝐷𝐷

𝑄𝑄𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤 = ℎ𝑐𝑐 ∙ 𝐴𝐴 ∙ (𝑇𝑇𝑤𝑤 𝑜𝑜𝑜𝑜𝑤𝑤 − 𝑇𝑇w in)

Heat

T1

T2

T3

T4

𝑄𝑄2 =𝑘𝑘 ∙ 𝐴𝐴 ∙ (𝑇𝑇3 − 𝑇𝑇4)

𝐷𝐷

Power density = mean {𝑄𝑄1𝐴𝐴

… 𝑄𝑄2𝐴𝐴

}

𝑇𝑇𝑐𝑐𝑜𝑜𝑐𝑐𝑤𝑤 1 = 𝑇𝑇2 − [ (𝑇𝑇1 − 𝑇𝑇2)

𝐷𝐷∙ 𝑑𝑑]

D

D d

𝑇𝑇𝑐𝑐𝑜𝑜𝑐𝑐𝑤𝑤 2 = 𝑇𝑇3 + [ (𝑇𝑇3 − 𝑇𝑇4)

𝐷𝐷∙ 𝑑𝑑]

𝑇𝑇CR =𝑇𝑇𝑐𝑐𝑜𝑜𝑐𝑐𝑤𝑤 1 − 𝑇𝑇𝑐𝑐𝑜𝑜𝑐𝑐𝑤𝑤 2

𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑑𝑑𝑃𝑃𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑

Sample 1

Sample 2

water

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First experimental test Samples and water cooling system assembling

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First experimental test Temperature sensors and assembled system

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T1 TC-K

T2 TC-K T3 TC-K T4 TC-K

T6 RTD

T2 TC-K

T3 TC-K

T4 TC-K

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First experimental test TCR vs Contact pressure

Conditions

Cooling of upper flange NO

Collimator YES

Lamp Voltage 50 V

Contact pressure [MPa] 4,2 → 1,3 → 4,2

Samples Cu (standard turning Ra~3-5µm)

Water flow rate 2.4 l/min

Water inlet temperature 20 °C

Repetition 4 runs

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First experimental test TCR vs Contact pressure trend

3,E-05

4,E-05

4,E-05

5,E-05

5,E-05

6,E-05

6,E-05

7,E-05

7,E-05

1 1,5 2 2,5 3 3,5 4 4,5

TC

R [

K·m

2 /W

]

Contact pressure [MPa]

TRC 1.1 TCR 1.2 TCR 1.3 TCR 1.4

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4,2 →1,3 →4,2 MPa

Basically NO hysteresis observed

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3,19E-05 3,39E-05

3,73E-05

4,21E-05

4,94E-05

6,20E-05

3,E-05

4,E-05

4,E-05

5,E-05

5,E-05

6,E-05

6,E-05

7,E-05

7,E-05

1 1,5 2 2,5 3 3,5 4 4,5

TC

R [

K·m

2 /W

]

Contact pressure [MPa]

First experimental test TCR vs Contact pressure trend

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First experimental test Comparison with analytical model

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𝑇𝑇𝑇𝑇𝑇𝑇 = 1,55 𝑘𝑘𝑠𝑠𝑚𝑚𝜎𝜎

2𝑝𝑝𝑚𝑚𝐸𝐸′

0,94

TCC: thermal contact conductance [W m-2 K-1]

ks: 390 [W m-1 K-1]

σ: 3 · 10-6 [m] (standard turning surface finishing)

m: 0,19

p: 4,2 · 106 [Pa]

E’: 117 · 109 [Pa]

TCC = 1,7 · 104 W m-2 K-1 →

TCRmodel = 5,8 · 10-5 m2 K W-1

Good matching between theoretical and experimental values

TCRexp = 3..4 · 10-5 m2 K W-1

Working Roughness Ra (µm)

Turning 0.2-6

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Thermal contact resistance at interface Expected values at fixed surface roughness

Pressure [MPa] TCR [K m2 W-1] ∆T expected [K]

4 2,0e-6 20

3 2,6e-6 26

2 3,8e-6 38

1 7,2e-6 72

0.5 1,4e-5 139

Cu-Cu, 0.1 µm, 1kW/cm2

Estimation of TCR vs Concact pressure

Taking into account a standard lapping surface finishing (Ra ~0.1 µm) the design specs may be achieved minimal interface temperature drop.

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Future plan

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TCR vs roughness (lapped, standard turning, mirror-like)

+ Al samples

Oxidized surfaces

Use of protective coating (Au)

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Future plan

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Additional prospective

Test particular cooling chamber system geometry (lamella, microchannel,

non-standard geometries prepared with Additional Manufacturing)

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Thank you for your

kind attention!